1. Field of the Invention
The present invention relates to a camera and a system that operate from a secondary battery.
2. Description of the Prior Art
In recent years, lithium-ion and other technologies have brought about dramatic advancements in the field of secondary batteries, making increasingly compact and high-capacity secondary batteries viable. Nowadays, even polymer-based secondary batteries are offered for practical use, which can be used in card-sized packages or even in other freely shaped pages. Thus, it is very likely that such secondary batteries will find effective applications in cameras, which also have been made increasingly compact in these days.
On the other hand, it is customary, in digital cameras, silver-halide film cameras (for example, lens-shutter cameras), and the like, to use wires and flexible circuit boards as a means of transferring image data and of supplying electric power.
FIG. 6 is a perspective view showing the appearance of an example of a conventional digital camera. The body 1 of this camera has, on its top surface, a release button 3. The body 1 has, on one side surface, fitting holes 1a that are used to fit a lens barrel 2 to the body 1. The lens barrel 2 has, on its outer surface, fitting pins 2a that are used to fit the lens barrel 2 to the body 1. The lens barrel 2 has, inside itself, a lens 6 and a CCD (not shown here) serving as an imaging device. The body 1 and the lens barrel 2 are connected together by a cable 4.
FIG. 6 shows the state of the camera with the lens barrel 2 detached from the body 1. Even in this state, it is possible to perform shooting by pressing the release button 3 with the lens barrel 2 pointing at an object (not shown). At this time, the image formed on the CCD provided inside the lens barrel 2 through the lens 6 is, in the form of image data, transferred to the body 1 by way of the cable 4. As shown in FIG. 7, the lens barrel 2 can be attached to the body 1 by engaging the fitting pins 2a with the fitting holes 1a.
FIG. 8 shows a vertical section, as seen from a side, of an example of a lens-shutter camera taken as an example of a conventional silver-halide film camera. This camera has a lens barrel 7 for housing lenses, a camera body frame 8, a circuit board 9 for mounting electronic components, a flexible circuit board 10 for securing electrical connection between the camera body and the lens barrel 7, a rotary barrel 1, a stationary barrel 12, a first lens unit 13, a second lens unit 14, a shutter 15, a first lens frame 16 for holding the first lens unit 13, and a second lens frame 17 for holding the second lens unit 14. The camera further has a pressing plate 30 for pressing a film (not shown), and a camera body cover 31. The camera body as a whole will be identified with the numeral 32.
In FIG. 8, when the rotary barrel 11 is rotated about the optical axis X by a driving mechanism (not shown), the lens barrel 7, together with the first lens frame 16 and the second lens frame 17 fixed inside it, moves along the optical axis X. This makes it possible to perform zooming, and to retract the lens barrel when so desired. FIG. 8 shows the state of the camera with the lens barrel 7 positioned at the telephoto end. Although not shown, the first lens frame 16 incorporates the driving mechanism for the first lens unit 13 and the driving mechanism for the shutter 15. Supply of electric power to these driving mechanisms, and exchange of various signals for them between the camera body and the lens barrel, is achieved by way of the flexible circuit board 10.
For example, in response to an instruction from the camera body 32, an electric current can be fed by way of the flexible circuit board 10 to instruct the shutter 15 to be released or shut, or to instruct the first lens unit 13 to be driven for focusing. In exchange, various control signals, such as a shutter pin hole detection signal and a movable lens initial position signal, can be fed from the lens barrel 7 to the camera body 32.
However, components such as a cable and a flexible circuit board that are used to achieve exchange of signals and supply of electric power have conventionally been causing a great deal of trouble in terms of space to be secured for them and malfunction such as wire breakage associated with them. For example, the above-described conventional digital camera shown in FIGS. 6 and 7 has the advantage of permitting shooting with the lens barrel 2 freely pointing at the object irrespective of the posture of the camera, but has the disadvantage of being prone to wire breakage in the cable 4. Moreover, even when the lens barrel 2 is attached to the body 1, the cable 4, which is difficult to keep in a rest position neatly, tends to be felt as a nuisance and thus remains prone to wire breakage.
On the other hand, in the above-described conventional lens-shutter camera shown in FIG. 8, the flexible circuit board 10 is, in a front portion of the camera body 32, connected to the circuit board 9. When the lens barrel 7 is at the telephoto end as shown in FIG. 8, the flexible circuit board 10 is in a slack state, and, as the lens barrel 7 is moved inward, the flexible circuit board 10 is brought into its rest position along the inner surface of the stationary barrel 12. Inconveniently, this structure requires delicate designing so that the flexible circuit board 10, when in a slack state, will not intercept the light from the object (indicated by the letter A in FIG. 8), and in addition so that the force applied to the flexible circuit board 10 as the lens barrel 7 is moved back and forth will not cause wire breakage.
Japanese Laid-Open Utility Model Applications Nos. S63-185356 and S63-185357 propose electronic viewfinders that can be used independently even when detached from the camera body. However, these applications give no mention of how their viewfinders are supplied with electric power.
In any event, most cameras are designed to operate from a battery that is commercially available anywhere, and in particular almost all of those designed for the general public are designed to operate from a commercially available battery.
In recent years, however, the size of such batteries has been hindering further miniaturization of cameras that is eagerly sought. This is because commercially available batteries have predetermined shapes, and this imposes various restrictions on the design of cameras that employ them. Thus, it is impossible to miniaturize cameras beyond certain limits. Moreover, attempting maximum miniaturization by the use of an extremely small battery ends in permitting too few images to be shot with that battery.
On the other hand, in cases where a camera employs a secondary battery that can be recharged for repeated use from an external electric power source, the shape of the battery can be designed comparatively freely, but the battery invariably occupies as much space as corresponds to its capacity. Moreover, once the battery becomes empty, it cannot be recharged unless supplied with electric power from the wall outlet. This may lead to wasted shooting opportunities, for example, on a trip.